This invention relates to a new polyurethane composition having improved flame retardancy and to a method for preparing such compositions.
Numerous attempts have been made in the prior art seeking solutions to improving flame retardancy for polyurethane compositions. Typically, these attempts have provided compositions which only limitly improve the flame retardant capacity while greatly increasing the cost of the final composition. It has now been found, however, that by practice of the present invention, there results a new improved flame retardant polyurethane which is easily prepared both commercially and economically.
Hydrophilic foams similar to those of the present invention are described in U.S. patent application Ser. No. 805,458 filed June 10, 1977 now U.S. Pat. No. 4,137,200 issued Jan. 30, 1979, wherein large amounts of water containing relatively large amounts of alumina hydrate are combined with hydrophilic urethane prepolymers under foam-forming conditions. The application also describes addition of fire-retardant additives to hydrophilic foams. Applicants are also aware of U.S. Pat. No. 3,262,894 describing the synergistic effect of alumina hydrate and phosphorus additives in urethane foams. The compounds are said to make said foams self-extinguishing under ASTM D1692-59T. This effect is achieved by employing from 11 to 30% by weight of the alumina hydrate, the weight percentage being based on the total dry foam weight.